Adapting to Survive: Carnivorous and Parasitic Plants
Carnivorous and parasitic plants are two great examples of how when faced with extinction, plants are not as passive as they may seem. There are several varieties suitable to be grown at home, both indoors and out.
Plants are often thought of as docile, passive creatures that are helplessly reliant on the soil in which they grow. However, some species of plants have shown that when necessary, they can develop some fascinating capabilities.
Speaking realistically, nature at its core is not kind. Plants and all other forms of life must adapt to survive and multiply. In the plant kingdom, the will and need to survive has triggered some unique adaptations, resulting in several different species of plants that beckon us to rethink everything we think we know about plant growth and survival. Two enticing examples are plants that have become carnivorous or parasitic.
There are more than 600 documented species of carnivorous plants worldwide spanning several different plant families. Carnivorous plants are most often flowering vascular plants with the ability to perform photosynthesis and receive mineral nutrients via their roots. Through the years, this type of plant has evolved the ability to capture and consume insects of various types and sizes.
Although there are many different types of traps, the circumstances that have led to this type of adaptation are similar in nearly every instance. Carnivorous plants are found growing in areas such as bogs and marshes that lack the proper amounts of mineral nutrients, mainly nitrogen and phosphorus, to encourage healthy plant growth and reproduction.
The development of insect traps was triggered by the lack of available nutrition in the soil. Traps include pitfall traps (pitcher plants), flypaper-style traps (sundews), snap traps (Venus flytraps), suction traps (bladderworts) and lobster-pot traps. Two popular carnivorous plants that can be grown at home both indoors and out are Venus flytraps and pitcher plants.
Pitcher plants are generally categorized into two main families—the old-world Nepenthaceae and the new-world Sarraceniaceae. The old-world species grow mainly in trees and develop a primitive-looking pitcher and the new-world species grow from rhizomes in the ground and form a more complex pitcher from an entire leaf. Pitcher plants are found all over the world in bogs and marshes with substandard sources of nitrogen.
Two popular species in North America are the Sarracenia and the Darlingtonia (native to northern California and Oregon). Both are members of the new-world family. Their pitchers create nectar that attracts insects. Once the insect is lured into the pitcher, the nectar traps them and an enzyme, much like our own digestive enzymes, slowly kills and breaks down the constituent proteins within the insect. After the proteins are completely broken down, the plant is able to use the nitrogen contained within. Pitcher plants can be grown at home both inside—under T5 florescent lights—and out.
The important thing to remember is to simulate their natural environment as closely as possible by using a growing medium that is inert and completely free of any mineral nutrient charge. Use absolutely NO fertilizer—pitcher plants have evolved into carnivorous plants due to an extreme lack of mineral nutrition and that is what they thrive on.
Venus flytraps are native to the nutrient-deficient swamplands and bogs of North and South Carolina. They prey on insects with the help of some uniquely shaped leaves—the leaf blade is comprised of two lobes hinged together at a midrib. The surface of the leaf has what are referred to as trigger hairs. When two or three of the trigger hairs are touched consecutively in a small amount of time, the trap snaps shut, confining the insect inside.
The trap is lined with teeth like cilia that interlock when the trap is closed, making escape for the insect nearly impossible. With the insect trapped inside, the leaf begins to create the digestive enzymes that will break the now-dead insect down into proteins and then into an available nitrogen source. Venus flytraps can also be grown at home inside (with artificial lighting) or out. Once again, use a potting soil that doesn’t have mineral nutrients and do not fertilize. Venus flytraps, as well as pitcher plants, can be watered frequently and grow well when consistently wet.
Most types of carnivorous plants are native to areas that are threatened by human development. This is why it is important to buy carnivorous plants for growing at home from reputable growers who start the plants by either splitting the rhizomes or from tissue culture propagation. In almost all cases, it is illegal to gather carnivorous plants from the wild and those who are caught doing so are levied with heavy fines.
This group of vascular plants has adapted the ability to fend for themselves in conditions that lack available nutrients or where the competition for nutrients is extreme. Parasitic plants vary from those that are fully photosynthetic to those that are just barely able to photosynthesize.
As the name implies, parasitic plants have circumvented the need to find nutrients in a small plot of soil by the development of a modified meristem root called a haustorium that can penetrate the vascular system of another plant, called a host, stealing vital mineral nutrients, water and carbohydrates for its own benefit. This type of interaction often results in fatality for the host plant.
Parasitic plants can attack a host in a variety of ways ranging from an attack on the roots to an attack on the vascular tissue found in the stems. Two examples of parasitic plants that are somewhat well known are the several different species of mistletoe and the dodder vine.
The dodder vine is a wispy plant with thin stems that attaches to a host plant’s stems via its haustorium (modified root). The haustorium will effectively reroute any water and mineral nutrients coming up from the roots as well as any carbohydrates coming down from the leaves—the product of photosynthesis—directly to the roots of the dodder plant. Dodder seeds are very small and contain little initial sustenance, so it is important the seedlings find a suitable host to feed upon within a few days or they may die.
The plant has the ability to aggressively attack a host, quickly engulfing it and eventually killing it. This is why the dodder plant is deemed a definite threat to agriculture, especially in developing countries, and requires a considerable amount of thought and attention on how to go about eradicating the plant from fields and pasture lands.
The plant family Loranthaceae includes multiple species of mistletoe, the most common of which is the species Phordendron serotinum—the eastern mistletoe, a staple of holiday seasons. Eastern mistletoe is a flowering vascular plant that grows on the branches of trees where mineral nutrients are not present. Mistletoe is able to perform photosynthesis, but it receives the majority of its mineral nutrient needs from the vascular system within the host tree’s branches.
This adaptation is likely due to the fact that after birds eat mistletoe berries, they often excrete the remaining seeds onto the branches of the trees they frequent. The mistletoe seeds in turn developed a sticky exterior that allows them to stick to the tree branches where they will germinate and grow.
Growing on the branches of a tree helps keep the mistletoe plants safe from possible predators, but this is also an environment nearly void of any mineral nutrition, so the plants parasitize the host tree and obtain needed nutrients to the detriment of the host.
The Will to Survive
Carnivorous and parasitic plants are two great examples of the fact that in nature, where the inability to adapt will almost certainly lead to the death of a species, plants are not as passive as they may seem.
Several species throughout many different plant families have taken survival into their own hands with the development of certain appendages that have truly changed the game in terms of normal plant behavior. These fascinating types of plants serve as unique reminders that nature, without compromise, is complex and constantly changing.